New memos state President George W Bush was suspended from flying for the Texas air national guard during the Vietnam war because he failed to meet their standards.

The documents released by the White House show the suspension also resulted from his failure to take his annual medical test as required.

The memos add details to the row over Mr Bush's military service in the war.

Their release came as Democrats stepped up their criticism of the president for allegedly failing to meet his duties.

With national security a key issue in the US presidential elections on 2 November, supporters of Mr Bush and Democratic nominee John Kerry are attacking each candidate's Vietnam records.

The BBC's Justin Webb in Washington says the Vietnam obsession is tiresome to many Americans, but it does matter, because both campaigns are using it to highlight what they believe are character defects in their opponents.

Republicans have attacked Mr Kerry's war service and Democrats have accused the president of ducking the draft call in favour of less dangerous duties.

We know John Kerry was in Vietnam," Democratic Party chief Terry McAuliffe said after reports that Mr Bush failed to complete required training, but was never disciplined.

"My question to you, Mr President, is, where were you, sir?

The White House has previously released some records to try to refute the charges.

Some experts have questioned the authenticity of the latest documents, released after they were obtained by CBS television.

Questions

Mr Bush trained as a pilot while a member of the Texas and Alabama air national guard but never flew in combat.

His suspension came as he was trying to arrange a transfer to a unit in Alabama to work on a political campaign in the state, the Associated Press reported.

Documents already released by the White House show that Mr Bush was suspended from flight status in 1972 for not having a medical test - but do not mention his alleged failure to comply with national guard standards.

CBS TV station reported on Wednesday night that it had obtained documents from Mr Bush's late Texas commander, saying Mr Bush discussed with him how to avoid drills during 1972.

Kerry has said Bush must come clean on what he did

In a memo, Lt Col Jerry Killian also said he was being pressured from his superior to give Mr Bush a positive evaluation.

Mr McAuliffe said Mr Bush's "cover story" is "rapidly unravelling".

But the White House Communications Director Dan Bartlett told CBS that President Bush had met his requirements "at every step of the way".

The White House later released the documents cited in the programme.

Some forensic experts were quoted by news organizations, including The Associated Press, saying the memos appeared to have been computer-generated with characteristics that weren't available three decades ago.

But CBS News said in a statement: "The documents are backed up not only by independent handwriting and forensic document experts but sources familiar with their content."

The new documents surfaced as the Bush administration released for the first time the president's personal flight logs.

Mr Bush left the national guard in 1973 to attend Harvard Business School.